/*
 * Copyright (c) 2002,2003, Stefan Haustein, Oberhausen, Rhld., Germany
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package base64;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Base64
{

    static final char[] charTab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

    public static String encode(byte[] data)
    {
        return encode(data, 0, data.length, null).toString();
    }

    /**
     * Encodes the part of the given byte array denoted by start and len to the
     * Base64 format. The encoded data is appended to the given StringBuffer. If
     * no StringBuffer is given, a new one is created automatically. The
     * StringBuffer is the return value of this method.
     */

    public static StringBuffer encode(byte[] data, int start, int len, StringBuffer buf)
    {

        if (buf == null)
            buf = new StringBuffer(data.length * 3 / 2);

        int end = len - 3;
        int i = start;
        int n = 0;

        while (i <= end)
        {
            int d = (((data[i]) & 0x0ff) << 16) | (((data[i + 1]) & 0x0ff) << 8) | ((data[i + 2]) & 0x0ff);

            buf.append(charTab[(d >> 18) & 63]);
            buf.append(charTab[(d >> 12) & 63]);
            buf.append(charTab[(d >> 6) & 63]);
            buf.append(charTab[d & 63]);

            i += 3;

            if (n++ >= 14)
            {
                n = 0;
                buf.append("\r\n");
            }
        }

        if (i == start + len - 2)
        {
            int d = (((data[i]) & 0x0ff) << 16) | (((data[i + 1]) & 255) << 8);

            buf.append(charTab[(d >> 18) & 63]);
            buf.append(charTab[(d >> 12) & 63]);
            buf.append(charTab[(d >> 6) & 63]);
            buf.append("=");
        }
        else
            if (i == start + len - 1)
            {
                int d = ((data[i]) & 0x0ff) << 16;

                buf.append(charTab[(d >> 18) & 63]);
                buf.append(charTab[(d >> 12) & 63]);
                buf.append("==");
            }

        return buf;
    }

    static int decode(char c)
    {

        if (c >= 'A' && c <= 'Z')
            return (c) - 65;
        else
            if (c >= 'a' && c <= 'z')
                return (c) - 97 + 26;
            else
                if (c >= '0' && c <= '9')
                    return (c) - 48 + 26 + 26;
                else
                    switch (c)
                    {
                    case '+':
                        return 62;
                    case '/':
                        return 63;
                    case '=':
                        return 0;
                    default:
                        throw new RuntimeException("unexpected code: " + c);
                    }
    }

    /**
     * Decodes the given Base64 encoded String to a new byte array. The byte
     * array holding the decoded data is returned.
     */

    public static byte[] decode(String s)
    {

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        try
        {

            decode(s, bos);

        }
        catch (IOException e)
        {
            throw new RuntimeException();
        }
        return bos.toByteArray();
    }

    public static void decode(String s, OutputStream os) throws IOException
    {
        int i = 0;

        int len = s.length();
        System.out.println("Length of string to be decoded:" + len);

        if ((len % 4) != 0)
        {
            len = len - (len % 4);
            System.out.println("Truncating string to length:" + len);
        }

        while (true)
        {
            while (i < len && s.charAt(i) <= ' ')
                i++;

            if (i == len)
                break;

            int tri = (decode(s.charAt(i)) << 18) + (decode(s.charAt(i + 1)) << 12) + (decode(s.charAt(i + 2)) << 6)
                    + (decode(s.charAt(i + 3)));

            os.write((tri >> 16) & 255);
            if (s.charAt(i + 2) == '=')
                break;
            os.write((tri >> 8) & 255);
            if (s.charAt(i + 3) == '=')
                break;
            os.write(tri & 255);

            i += 4;
        }
    }
}
